This invention relates to a hydraulic system for a vehicle, such as a tractor, and, more particularly, a hydraulic utility system for supplying a pressurized fluid to a number of user devices on the vehicle, including two axles, each having at least one wheel; a brake assembly for each of the two axles; and a valve for selectively controlling operation of a first of the brake assemblies in response to a signal from a second of the brake assemblies.
The valve means normally comprise a tubular body with a longitudinal axis; and a piston fitted to slide axially inside the tubular body and shaped to define, together with the tubular body, a first, a second, and a third variable-volume chamber arranged successively in that order along the longitudinal axis.
More specifically, the first chamber receives the signal from the second brake assembly; the second chamber communicates with the hydraulic utility system; and the third chamber has an inlet communicating with an oil supply tank, and an outlet communicating with the first brake assembly.
In response to the signal from the second brake assembly, the piston is moved along the longitudinal axis to connect the second chamber to the hydraulic utility system, so that the total pressure exerted on the piston by the pressurized oil fed to the first and second chambers compresses the oil fed to the third chamber from the supply tank, so as to activate the first brake assembly.
A major drawback, therefore, of known vehicles of the above type lies in the valve means being relatively complex and expensive, by requiring a supply tank and a relatively large number of hydraulic connecting pipes, and therefore being difficult to install, especially on vehicles in which the first brake assembly is an optional as opposed to a standard part.
It is an object of the present invention to provide a vehicle, in particular a tractor, designed to eliminate the aforementioned drawbacks.
According to the present invention, there is provided a vehicle having a hydraulic utility system for supplying pressurized fluid to a number of user devices, including two axles, each having at least one wheel; and a brake assembly for each of the axles. A first valve mechanism feeds pressurized fluid directly to a first of said brake assemblies in response to a signal from a second of the brake assemblies.
These and other objects, features and advantages are accomplished according to the instant invention by providing a vehicle that has a hydraulic utility system for supplying a pressurized fluid to a number of user devices including two axles, each having at least one wheel; a brake assembly for each of the axles; and a valve to feed the pressurized fluid of the hydraulic system directly to one of the two brake assemblies in response to a signal from the other of the two brake assemblies.